This invention relates to cable glands.
Cable glands for connecting an electric cable to a piece of equipment such as a junction box are known for use in hazardous environments to provide a sealed entry for the cable to contain any explosion occurring within the equipment.
The seal may be of the compression type in which relative rotation of two threadably engaged parts of the gland compresses the seal inwardly to bear onto the surface of the cable. This type of seal has to be matched to the size of the cable and use of the incorrect seal can result in poor sealing efficiency. In addition, the compression force can result in the surface of the cable becoming deformed with subsequent loss of sealing efficiency if the gland is taken apart for inspection and then re-assembled.
These problems are largely avoided by a diaphragm type of seal in which an opening in the seal adapts automatically to different sizes of cable. A cable gland with this type of universal seal is the subject matter of our granted UK Patent No. 2276777-B.
We have now found, however, that during assembly of such glands having a universal seal, the marginal edge of the opening in the seal can be damaged by contact with the sharp conductor cores and/or rough edges of the cut end of the cable sheath as it is pushed through the opening. Such damage reduces sealing efficiency and, in certain cases, the seal may not meet safety requirements requiring the seal to be replaced which is time consuming.
The same problem can arise but usually to a lesser extent with seals of the compression type. For this reason, it has been the practice, whichever type of seal is used, to cover the cut end of the cable with an adhesive tape to reduce the risk of damage to the seal. Often the glands are assembled in conditions of restricted space and/or visibility with the result that the taping of the cut end of the cable and subsequent removal of the tape is awkward and adds considerably to assembly time.
The present invention has been made from a consideration of the foregoing problems and disadvantages of known cable glands.